1. Field of the Invention
The present invention relates to an inkjet recording head which has a nozzle which ejects ink drops, a pressure chamber which communicates with the nozzle and in which ink is filled, a vibrating plate structuring a portion of the pressure chamber, an ink pooling chamber which pools ink to be supplied to the pressure chamber via an ink flow path, and a piezoelectric element which displaces the vibrating plate, and to an inkjet recording device which uses this inkjet recording head. The present invention also relates to the piezoelectric element used therein.
2. Description of the Related Art
There have conventionally been known inkjet recording devices in which characters, images or the like are printed onto a recording medium such as a recording sheet or the like which is conveyed-in along a subscanning direction, by ejecting ink drops selectively from plural nozzles of an inkjet recording head (hereinafter, simply called “recording head” upon occasion) which moves reciprocatingly in a main scanning direction.
Such an inkjet recording device has piezoelectric system recording heads, thermal system recording heads, or the like. For example, in the case of a piezoelectric system recording head, as shown in FIGS. 14 and 15, a piezoelectric element (an actuator which converts electrical energy into mechanical energy) 206 is provided at a pressure chamber 204 to which ink 200 is supplied from an ink tank via an ink pooling chamber 202. The piezoelectric element 206 flexurally deforms in a concave form so as to reduce the volume of the pressure chamber 204, thereby applying pressure to the ink 200 therein and ejecting the ink 200 as an ink drop 200A from a nozzle 208 which communicates with the pressure chamber 204.
Various proposals have been made for the purpose of improving the ink-resistance and the moisture-resistance of the structural members of the recording head (and the piezoelectric element in particular).
For example, Japanese Patent Application Laid-Open (JP-A) No. 3-166953 proposes covering the electrode surface of a piezoelectric element with an organic high polymer compound, so as to ensure the ink-resistance. JP-A No. 10-226071 proposes forming a silicon oxide or polyimide resin film on a piezoelectric element, so as to improve the moisture-resistance. JP-A No. 11-334061 discloses providing a flexible sealing film on the top portion of a piezoelectric element in order to improve the moisture-resistance of the piezoelectric element and prevent impeding of displacement of the piezoelectric element at the same time. JP-A No. 7-10157 proposes successively layering an organic film for mitigating stress, an inorganic film for improving the moisture-resistance, and an organic film for making the surface smooth, on the pressure chamber side surface of the piezoelectric element so as to protect this surface of the piezoelectric element. JP-A No. 2001-88296 discloses using an electrically-conductive metal oxide film at an electrode in order to improve the moisture-resistance.
However, due to the current demands for high technology, even these proposals are insufficient, and further improvements are needed.